/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.activiti.engine.delegate.event.impl;

import org.activiti.engine.delegate.event.*;
import org.activiti.engine.impl.context.Context;
import org.activiti.engine.impl.interceptor.CommandContext;
import org.activiti.engine.impl.persistence.entity.ProcessDefinitionEntity;
import org.activiti.engine.repository.ProcessDefinition;

/**
 * Class capable of dispatching events.
 *
 * @author Frederik Heremans
 */
public class ActivitiEventDispatcherImpl implements ActivitiEventDispatcher {

    protected ActivitiEventSupport eventSupport;
    protected boolean enabled = true;

    public ActivitiEventDispatcherImpl() {
        eventSupport = new ActivitiEventSupport();
    }

    public boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    @Override
    public void addEventListener(ActivitiEventListener listenerToAdd) {
        eventSupport.addEventListener(listenerToAdd);
    }

    @Override
    public void addEventListener(ActivitiEventListener listenerToAdd, ActivitiEventType... types) {
        eventSupport.addEventListener(listenerToAdd, types);
    }

    @Override
    public void removeEventListener(ActivitiEventListener listenerToRemove) {
        eventSupport.removeEventListener(listenerToRemove);
    }

    @Override
    public void dispatchEvent(ActivitiEvent event) {
        if (enabled) {
            eventSupport.dispatchEvent(event);
        }

        // Check if a process context is active. If so, we also call the
        // process-definition specific listeners (if any).
        if (Context.isExecutionContextActive()) {
            ProcessDefinitionEntity definition = Context.getExecutionContext().getProcessDefinition();
            if (definition != null) {
                definition.getEventSupport().dispatchEvent(event);
            }
        } else {
            // Try getting hold of the Process definition, based on the process
            // definition-key, if a context is active
            CommandContext commandContext = Context.getCommandContext();
            if (commandContext != null) {
                ProcessDefinitionEntity processDefinition = extractProcessDefinitionEntityFromEvent(event);
                if (processDefinition != null) {
                    processDefinition.getEventSupport().dispatchEvent(event);
                }
            }
        }
    }

    /**
     * In case no process-context is active, this method attempts to extract a
     * process-definition based on the event. In case it's an event related to an
     * entity, this can be deducted by inspecting the entity, without additional
     * queries to the database.
     * <p>
     * If not an entity-related event, the process-definition will be retrieved
     * based on the processDefinitionId (if filled in). This requires an
     * additional query to the database in case not already cached. However,
     * queries will only occur when the definition is not yet in the cache, which
     * is very unlikely to happen, unless evicted.
     *
     * @param event
     * @return
     */
    protected ProcessDefinitionEntity extractProcessDefinitionEntityFromEvent(ActivitiEvent event) {
        ProcessDefinitionEntity result = null;

        if (event.getProcessDefinitionId() != null) {
            result = Context.getProcessEngineConfiguration().getDeploymentManager().getProcessDefinitionCache()
                    .get(event.getProcessDefinitionId());
            if (result != null) {
                result = Context.getProcessEngineConfiguration().getDeploymentManager().resolveProcessDefinition(result);
            }
        }

        if (result == null && event instanceof ActivitiEntityEvent) {
            Object entity = ((ActivitiEntityEvent) event).getEntity();
            if (entity instanceof ProcessDefinition) {
                result = (ProcessDefinitionEntity) entity;
            }
        }
        return result;
    }

}
